1. Field of the Disclosure
The present disclosure relates to a vacuum interrupter for enhancing arc extinction and break performance.
2. Background of the Disclosure
Generally, a vacuum circuit breaker is a type of circuit breaker that is provided in a high-voltage power system, and when a risk condition such as short circuit or an overcurrent occurs, breaks a circuit to protect the power system. The vacuum circuit breaker is designed to have excellent insulation performance and arc extinction capability in a vacuum state.
The vacuum circuit breaker includes a vacuum interrupter as an essential element. The vacuum interrupter includes a fixing electrode, which performs an electricity conducting function and break function of a circuit in a sealed vacuum tube, and a movable electrode which may contact the fixed electrode or may be separated from the fixed electrode. In particular, a portion at which the fixed electrode directly contacts the movable is referred to as a contact. A high current flows in a contact of a circuit. When a flat contact in which any design is not reflected in a contact is used, a high-temperature arc is contracted by contact separation, and is fixed to the center of the float contact. This is referred to as a pinch effect. In order to prevent the pinch effect, an axial magnetic field and a radial magnetic field have been proposed as a contact shape. The axial magnetic field uses a method that immediately spread arcs to prevent the arc from being contracted, and the radial magnetic field uses a method that allows an arc to be contracted but rotates the arc to disperse arc energy.
A vacuum interrupter using the axial magnetic field has an axial magnetic electrode structure, which rotates a current in a circumference direction of an electrode to generate a magnetic flux in an axial direction, between a fixed electrode and a movable electrode. The axial-direction magnetic flux spread arcs, which are generated between electrodes, to a whole surface of an electrode contact surface, and thus prevents an electrode surface from being damaged by a concentration of arcs and enables a current to be cut off.
The axial magnetic structure is categorized into a coil type electrode structure illustrated in FIG. 1 and a cup type electrode structure illustrated in FIG. 2. In the coil type electrode structure of FIG. 1, a current conducting path of an electrode is formed in a coil shape, and an axial-direction magnetic flux is generated in an electrode surface. In the cup type electrode structure of FIG. 2, an inclined slit is provided in a cup-shaped hollow conductor, and an axial-direction magnetic flux is generated by flowing a current through the slit.
An example of FIG. 1, a current flowing into an electrode supporting plate 3 generates a current I which rotates in a circumference direction through a plurality of coil electrodes 1 and 2 connected to a plurality of lower conductor connection pins 4 and 6. The current I flows to a contact electrode (not shown) through a plurality of upper conductor connection pins 5 and 7, and then flows to another electrode facing the contact electrode. Here, a magnetic field is generated in an axial direction with the current I which flows in the coil electrodes 1 and 2.
An example of FIG. 2, a plurality of slits 12 are formed in a diagonal direction in a cup-shaped conductor 11, and thus, an electricity conducting path 13 through which a current flows is formed. A current I flowing through the electricity conducting path 13 flows to another facing electrode through a contact (not shown). Here, an axial-direction magnetic field is generated with the current I which flows through the electricity conducting path 13.
In directions of the currents respectively illustrated in FIGS. 1 and 2, the currents flow in the same direction or a single direction, and thus, as illustrated in FIG. 3, an axial-direction magnetic flux B generated between a fixed electrode 31 and a movable electrode 32 is generated in a single direction. FIG. 3 illustrates a distribution of unidirectional magnetic flux densities.
FIG. 4 is a plan view illustrating an example of a contact electrode used in the coil type electrode structure of FIG. 1. An intensity of the magnetic flux which is generated in the axial direction is changed depending on a change in a current, and the change in the magnetic flux generates an eddy current 42 in a surface of a contact electrode 40. The eddy current 42 causes a phase difference between a current and a magnetic flux, and a remaining magnetic flux is generated at a current zero, thereby affecting arc extinction.
As illustrated in FIG. 4, four slits 41 are formed in a contact electrode 40 in which a unidirectional axial magnetic field is formed, for preventing the eddy current 40 from being generated.
However, in a prior art coil type axial magnetic field electrode structure, since the number (for example, four) of the slits 41 formed in the contact electrode 40 is excessive, a process time is extended, and the manufacturing cost increases.
Moreover, dielectric strength is reduced due to a local concentration of an electric field caused by a shape of a slit.